When repairing a brick wall, first clear out all damaged bricks, and clean out the old mortar. It is best to use a power drill and masonry cutting wheel to remove the bricks, but a chisel and heavy hammer work as well, although removing bricks with a chisel usually takes longer. Use a chisel to clean out the old mortar, and rinse the bricks with water to remove dust or dirt.
When mixing new mortar, make sure its color matches the color of mortar in the brick wall. Cover the bottom and sides of the opening in the wall with a layer of mortar about 1 inch thick. Use a pointing trowel to apply it.
Make sure to moisten each brick before setting it in place. Cover its sides with mortar, slide it into the opening in the wall, and clean off excess mortar. After all new bricks are in place, keep new bricks and mortar moist until the mortar dries completely, which usually takes three days. This ensures the mortar cures properly.
Always use protective goggles and gloves when conducting repairs. Before starting the repair, make sure the bricks you've picked out are the same size and color as the old bricks in the wall.